&nbsp234 &nbspFXSA20 KWBC 301705 &nbspPMDSA &nbsp &nbspSOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS &nbspNWS WEATHER PREDICTION CENTER COLLEGE PARK MD &nbsp1205 PM EST THU NOV 30 2017 &nbsp &nbspGFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/ &nbsp &nbspMODEL DISCUSSION (VALID FROM NOV 30 AT 0000 UTC): MODELS ONCE &nbspAGAIN MAKE PATTERN CORRECTIONS TO THE SOUTHERN STREAM FLOW DURING &nbspTHE MEDIUM RANGE PERIOD...WITH THE GFS NOW FAVORING A &nbspSLOWER/HIGHER AMPLITUDE TROUGH TO ENTER THE SOUTHERN CONE LATER &nbspDURING THE WEEKEND. IN CONTRAST...THE EUROPEAN MODELS NOW FORECAST &nbspA SLIGHTLY FASTER/LOWER AMPLITUDE PERTURBATION. IN THIS PERIOD THE &nbspVARIABILITY AMONG THE ENSEMBLE MEMBERS IS TOO HIGH TO ESTABLISH &nbspCONFIDENCE ON EITHER SOLUTION. SO FURTHER CORRECTIONS ARE EXPECTED. &nbsp &nbspFLOW OVER THE WESTERN ATLANTIC SPLITS BETWEEN A RIDGE ON THE &nbspSOUTHERN STREAM AND A SHORT WAVE TROUGH TO THE NORTH. THE RIDGE &nbspEXTENDS SOUTH OF 40S AND ALONG 30W/35W TO 75S. UNDER INFLUENCE OF &nbspSHORT WAVE PERTURBATIONS STREAMING ACROSS THE DRAKE &nbspPASSAGE/SOUTHERN CONE...THE RIDGE IS FORECAST TO GRADUALLY FLATTEN &nbspEARLY ON SATURDAY MORNING. THE TROUGH TO THE &nbspNORTH...MEANWHILE...IS TO EXTEND BETWEEN 55W-25W...WHILE CENTERING &nbspON A CLOSED LOW AT 33S 42W. THROUGH SUNDAY EVENING THE SHORT WAVE &nbspTROUGH IS TO WEAKEN WHILE SHEARING SHORT WAVE ENERGY TO THE &nbspSOUTH-SOUTHEAST. MEANWHILE...THIS IS TO INTERACT WITH MEANDERING &nbspFRONT OVER THE WESTERN ATLANTIC. THE SURFACE FRONT EXTENDS TO THE &nbspNORTHWEST ACROSS RIO DE JANEIRO/SOUTHERN MINAS GERAIS TO MATO &nbspGROSSO DO SUL-CHACO PARAGUAYO. THE MID LEVEL TROUGH IS TO INTERACT &nbspWITH THIS BOUNDARY...TRIGGERING AN MCS ACROSS CHACO &nbspPARAGUAYO-SANTA CRUZ IN EASTERN BOLIVIA-MATO GROSSO DO SUL EARLY &nbspON FRIDAY MORNING. IN THIS AREA THIS IS TO FAVOR RAINFALL MAXIMA &nbspOF 75-125MM LATER ON FRIDAY/EARLY ON SATURDAY MORNING. OVER MINAS &nbspGERAIS-NORTHERN SAO PAULO THE MAXIMA IS TO INITIALLY PEAK AT &nbsp30-60MM. ON FRIDAY-SATURDAY THIS INCREASES TO 40-80MM...WHILE ON &nbspSATURDAY-MONDAY IT IS TO PEAK AT 30-60MM/DAY. &nbsp &nbspANOTHER MID LEVEL SHORT WAVE TROUGH ON THE NORTHERN STREAM EXTENDS &nbspOVER THE FAR EASTERN PACIFIC WITH AXIS NORTH ALONG 80W TO 30S. &nbspTHIS IS TO REMAIN STATIONARY WHILE SHEARING SHORT WAVE ENERGY &nbspACROSS CENTRAL-NORTHERN CHILE TO ARGENTINA. AT LOW LEVELS THE &nbspTROUGH SUSTAINS A SURFACE FRONT ACROSS LA PAMPA IN ARGENTINA TO &nbspCENTRAL REGIONS OF CHILE. THIS MEANDERS NORTH TO THE BUENOS AIRES &nbspPROVINCE/ MENDOZA IN ARGENTINA LATER ON THURSDAY. LATER ON SUNDAY &nbspIT IS TO THEN UNDULATE NORTH ACROSS PARAGUAY. THE TROUGH ALOFT IS &nbspINTERACTING WITH A SURFACE FRONT THAT MEANDERS OVER CENTRAL &nbspARGENTINA. LATER ON SATURDAY THE WEAK BAROCLINIC BOUNDARY MOVES &nbspNORTH ACROSS CENTRAL ARGENTINA...REACHING SOUTHERN BRASIL-URUGUAY &nbspON SUNDAY. OVER LA PAMPA-NORTHERN CUYO THIS IS TO FAVOR MAXIMA OF &nbsp20-40MM/DAY. ON FRIDAY-SATURDAY THIS INCREASES TO 25-50MM WHILE &nbspBUILDING NORTH ACROSS ARGENTINA TO PARAGUAY AND CORRIENTES IN &nbspARGENTINA &nbsp &nbspMID/UPPER LEVEL SHORT WAVE RIDGE IS TO THEN ESTABLISH ACROSS THE &nbspEASTERN PACIFIC. AS THE RIDGE HOLDS...IT IS TO FOCUS SHORT WAVE &nbspENERGY ACROSS CENTRAL CHILE TO ARGENTINA. THIS WILL COMBINE WITH A &nbspMOIST NORTHERLY FLOW TO LIKELY FAVOR SCATTERED DEEP CONVECTION &nbspACROSS CENTRAL/INTERIOR PORTIONS OF PUERTO RICO ON FRIDAY AND &nbspSATURDAY. &nbsp &nbspBROAD CELL OF THE SUBTROPICAL RIDGE EXTENDS AT 200 HPA OVER &nbspNORTHERN SOUTH AMERICA WHILE CENTERING ON A CLOSED HIGH OVER &nbspNORTHERN BOLIVIA. THIS IS TO PERSIST DURING THE NEXT FEW DAYS. AS &nbspTHE RIDGE HOLDS...IT IS TO VENT DIURNAL CONVECTION ACROSS &nbspBRASIL-PERU-ECUADOR/SOUTHERN COLOMBIA. THE MOST ACTIVE IS TO &nbspCLUSTER ALONG AND NORTH OF THE AFOREMENTIONED SURFACE FRONT OVER &nbspBRASIL-PARAGUAY/BOLIVIA. OTHER CONVECTION IS EXPECTED ACROSS PARA &nbspIN BRASIL TO FAVOR MAXIMA OF 20-30MM/DAY IN SCATTERED DEEP &nbspCONVECTION. OVER ACRE-AMAZONAS IN WESTERN BRASIL TO THE NORTHERN &nbspJUNGLE OF PERU/EASTERN ECUADOR EXPECTING MAXIMA OF 10-15MM/DAY. &nbspTHROUGH SATURDAY THIS IS TO INTENSIFY...WITH MAXIMA OVER &nbspAMAZONAS-SOUTHERN COLOMBIA-NORTHERN JUNGLE OF PERU TO PEAK AT &nbsp20-40MM. ON THE HIGH JUNGLE OF PERU...MEANWHILE...THE DAILY MAXIMA &nbspIS TO PEAK AT 20-30MM ON SATURDAY. &nbsp &nbspOVIEDO...SHN (ARGENTINA) &nbspVANNUCCI...SMN (ARGENTINA) &nbspRIVAS...SENAMHI (PERU) &nbspDAVISON...WPC (USA) &nbsp &nbsp